This study aimed to investigate the treatment efficiency of a synthetic dye solution in an anaerobic-aerobic combined reactor system, using pretreated residual yeast as a nutrient source and redox mediator. The applicability of the residual yeast as a nutrient source was firstly evaluated in anaerobic batch tests. Subsequently, two continuous bench-scale treatment settings were studied: (1) an Upflow Anaerobic Sludge Blanket (UASB) reactor followed by an activated sludge system and, (2) a UASB reactor followed by a shallow polishing pond. The two system configurations were fed with a synthetic azo dye solution of Yellow Gold Remazol (50 mg/L) and pretreated residual yeast (350 mg/L). According to the results, the UASB/shallow polishing pond-combined reactor attained the best values of chemical oxygen demand (COD) (85%) and dye removal (23%).

BACKGROUND Coffee husks (CH) are an abundant lignocellulosic residue that can be converted into biofuels and bioproducts through sustainable and economical processes in a biorefinery approach. For that, steam explosion (SE) pretreatment stands out as a technique to overcome its recalcitrant nature and enable byproduct valorization. In this study, solid and liquid fractions were separated after pretreatment for saccharification and biogas production, respectively. The research relevance relies on the contribution to environment decarbonization and monetization of decarbonization credits (CBIO) generated from the production of renewable fuel from waste biomass under different operational conditions (with and without pretreatment). RESULTS Liquid hydrolysate generated by SE condition at 210 °C and 15 min led to the highest biomethane production (292 NmL CH4 g CODfed−1). Similarly, high‐severity pretreatment also favored the enzymatic hydrolysis yield of the solid fraction (49%). In terms of environment decarbonization, SE promoted not only a lower carbon intensity when compared to the process without any pretreatment (3.8 vs. 6.4 g CO2eq MJ−1), but also increased the monetization of decarbonization credits by 175%, which represented a potential revenue of US $1 481 330. CONCLUSION High temperatures of SE pretreatment of CH at 210 °C were able to promote biogas production and fermentable sugars. In addition, the process reduced carbon emissions and increased the revenue from CBIO commercialization. Therefore, SE proved to be a sustainable and economic alternative for consideration in new green businesses from lignocellulosic residues such as CH. © 2021 Society of Chemical Industry (SCI).

A novel magnetic, structured (with ordered pores) and hybrid imprinted polymer (HMMIP) was synthesized to selectively adsorb volatile fatty acids (VFAs) from aqueous matrices. Usual characterization techniques showed that a mesoporous adsorbent was obtained with relatively low specific areas but that could selectively (imprinting factor of 1.64) remove isovaleric acid (used as template) from aqueous solutions and effluents containing VFAs with a good capacity (Qe ~ 50 mg g−1). From kinetic studies a pseudo‐nth‐order model showed the best fit to the experimental data and resulted in k n = 3 equal to 8 × 10−4 g mg−1 min−1 whereas thermodynamic studies indicated that the adsorption of isovaleric acid onto HMMIP was endothermic and entropically driven. Reuse studies indicated that HMMIP loaded with VFA could be efficiently regenerated with acetone–water solution which led to an adsorption loss of ca 10% after three regeneration/reuse cycles and that the magnetic and specific adsorbent could be removed from complex matrices with an efficiency of ca 77%. Biochemical methane production assays showed that the addition of HMMIP to anaerobic batch reactors increased by four times the methane production due to the selective adsorption of VFAs. © 2020 Society of Chemical Industry

Sugars released by thermochemical pretreatment of lignocellulosic biomass are possible substrate for hydrogen production. However, the major drawback for bacterial fermentation is the toxicity of weak acids and furan derivatives normally present in such substrate. This study aimed to investigate the metabolism involved in hydrogen production by the isolate Enterobacter LBTM2 using 10, 20 and 30-fold diluted synthetic (SH) and sugarcane bagasse hemicellulose (SBH) hydrolysates. In addition, the effects of acetic acid, formic acid and furfural on the bacterial metabolism, as well as detoxification of SBH with activated carbon and molecularly imprinted polymers on the hydrogen production were assessed. The results showed the best hydrogen yield was 0.46 mmol H 2 /mmol sugar for 20-times diluted SH, which was 2.3-times higher than obtained in SBH experiments. Bacterial growth and hydrogen production were negatively affected by 0.8 g/L of acetic acid when added alone, but were totally inhibited when formic acid (0.4 g/L) and furfural (0.3 g/L) were also supplied. However the maximum hydrogen production of SBH20 has duplicated when 3% of powdered activated carbon was added to the SBH experiment. The results presented herein can be helpful in understanding the bottlenecks in biohydrogen production and could contribute towards development of lignocellulosic biorefinery.

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